1. Field of the Invention
The present invention generally relates to jitter compensation in receiver circuits. Specifically, the present invention provides a system and method for jitter compensation in receiver circuits using nonlinear dynamic phase shifting technique based on bit history pattern.
2. Related Art
Intersymbol interference (ISI) is one of the main reasons for jitter in high speed serial links. In telecommunication, ISI means a form of distortion of a signal that causes the previously transmitted symbols to have an effect on the currently received symbol. This is usually an unwanted phenomenon as the previous symbols have similar effect as noise, thus making the communication less reliable. ISI is usually caused by echoes or non-linear frequency response of the channel and results in “jitter” or can be caused by other issues, such as reflections or refractions in the channel, etc. Jitter is an unwanted variation of one or more signal characteristics in electronics and telecommunications. Jitter can also be described as a combination of random and deterministic jitter. Jitter may be seen in characteristics such as the interval between successive pulses, or the amplitude, frequency, or phase of successive cycles. Jitter in high speed electrical interfaces causes uncertainty in the capture of incoming data that may lead to errors. Some of the known solutions to this issue include linear equalization methods such as Feed Forward Equalization (also known as pre-emphasis/de-emphasis), Decision Feedback Equalization (DFE), discrete equalization using RC/RLC networks as well as distributed equalization such as that found in Gore's Eye Opener Plus (EOP) cables address a loss induced by ISI. All these approaches are complex and, most of the time, they compensate attenuation significantly (eye height) and not jitter (eye width). In telecommunication, an eye pattern, also known as an eye diagram is an oscilloscope display in which a digital data signal from a receiver is repetitively sampled and applied to the vertical input, while the data rate is used to trigger the horizontal sweep. It is so called because, for several types of coding, the pattern looks like a series of eyes between a pair of rails. As noted above, jitter is measured by the eye width—not the eye height, which is what the prior art addresses. As shown in FIG. 1, eye pattern 100 has an eye height 102 and an eye width 104. Eye width 104 is shown as having a value of 210 ps (picoseconds).
There is a present need for a simple, easy to implement method and apparatus to reduce jitter in a channel and expand the eye width of the eye pattern.